Aquarium filter



FIG. 1 is a front elevation view of an aquarium filter showing my new design in which the height of the filter can be altered, without departing from the new design, by variation of the height of the central portion of the filter;

FIG. 2 is a right side elevation view of the filter;

FIG. 3 is a rear elevation view of the filter;

FIG. 4 is a left side elevation view of the filter;

FIG. 5 is a top plan view of the filter; and,

FIG. 6 is a bottom plan view of the filter. 

The ornamental design for aquarium filter, as shown and described. 